Wastewater treatment system and method

ABSTRACT

Disclosed is a system and method for treating municipal and sanitary wastewater. The system includes a three-output axial-flow type separator that separates wastewater into at least three fluid streams according to the specific gravity of the solids within the fluid streams. The lighter-than-water and heavier-than-water solids streams are combined and the resultant combination capable of being mechanically dewatered without intermediary biological-process systems. The system advantageously simplifies municipal and sanitary wastewater treatment by potentially eliminating traditional primary and secondary treatment stages, and significantly reducing the system&#39;s operational footprint. The system and method can be scaled to very large municipal systems.

CROSS REFERENCE

This application is a continuation-in-part of U.S. patent application Ser. No. 15/276,395 filed on Sep. 26, 2016, which is a continuation-in-part of U.S. patent application Ser. No. 15/018,863 filed on Feb. 8, 2016 now issued as U.S. Pat. No. 9,487,425 issued on Nov. 8, 2016. The entire contents of U.S. patent application Ser. No. 15/018,863 and U.S. patent application Ser. No. 15/276,395 are hereby incorporated by reference with differences between U.S. patent application Ser. No. 15/018,863 and the present disclosure and differences between U.S. patent application Ser. No. 15/276,395 and the present disclosure superseded by the present disclosure.

FIELD OF INVENTION

The present disclosure relates to a system and method for treating sanitary and municipal wastewater using centrifugal separation.

BACKGROUND

Municipal wastewater generally is piped from homes and businesses through a sewer piping system to a municipal wastewater treatment plant. In many towns and cities, storm water runoff infiltrates the sewer piping system. Municipal wastewater typically includes human urine and feces, food waste, household chemicals, and paper products such as toilet paper, tampons, and sanitary napkins. When mixed with storm water runoff, municipal wastewater can also include other litter and debris.

One of the purposes of treating municipal and sanitary wastewater is to allow sewage to be disposed without danger to human health or damage to the environment. Municipal wastewater is typically composed of approximately 99.8% to 99.9% water. The other 0.1% to 0.2% of municipal wastewater includes contaminants such as grit, fats and oils, oxygen-demanding substances, pathogens, plant nutrients, inorganic chemicals, and synthetic organic chemicals. One of the basic strategies of municipal and sanitary wastewater treatment is to remove or neutralize these contaminants and either dispose or reuse the water.

A typical municipal wastewater treatment process includes the following stages: pre-treatment, primary treatment, secondary treatment, tertiary treatment, and sludge treatment. The purpose of primary, secondary, and tertiary treatment is to remove and neutralize solids and pathogens so that the remaining water can be either reused or disposed of safely into the environment. The removed solids are known as sludge. The purpose of sludge treatment is to sufficiently dewater the sludge and neutralize the pathogens in the sludge so that the dewatered sludge can be safely recycled or disposed of.

Pre-treatment removes gross particulates and grit that can interfere with primary and secondary treatment processes. Primary treatment, also known as primary sedimentation, typically uses gravity to remove heavier-than-water solids, typically, in a basin or tank. The heavier-than-water solids settle to the bottom of the tank and are scraped and drained. The floating debris is skimmed from the top, passing over a weir. These solids are known as primary sludge.

Secondary treatment removes additional suspended solids and dissolved biodegradable material. This is typically accomplished using aerobic, or oxygen consuming, microorganisms to consume the soluble organic contaminants and other biodegradable material.

Tertiary treatment takes the product water from the secondary treatment and prepares it for reuse or for release into the environment. Tertiary treatment can remove remaining biological oxygen demand (BOD) dissolved solids, metals, pharmaceuticals, pesticides, and endocrine disruptors. There are a number of possible strategies for tertiary treatment. These can include media filtration, membrane filtration, ammonia and phosphate removal, and chemical disinfection.

The sludge can be biologically processed by either aerobic or anaerobic bacteria. The thickened sludge resulting from this operation typically has a solids concentration of 0.5% to 1% of solids to water. This sludge is further dewatered typically using a sludge filter press or a sludge-dewatering centrifuge. Both sludge filter presses and sludge-dewatering centrifuges require a minimum of 0.5% to 1% solids to water concentration for proper operation. The output of the dewatering process has approximately 15% to 35% solids to water concentration and typically is heat sterilized before disposal.

SUMMARY

As late as Feb. 25, 2015, the inventor utilized a three-output Richter-type separator in a municipal wastewater treatment for experimental testing at the Palm Beach County Western Region Wastewater Treatment Plant in Pahokee, Fla. As used in throughout this disclosure, a Richter-type separator is defined as an axial-flow type separator for separating immiscible fluids, or for separating solids in a fluid carrier, having different specific gravities and including a discharge manifold body connected to the fluid pump for drawing solids components having heavier specific gravities, where fluid pump employs an impeller having a hollow core for passing fluid from an inlet, the impeller having a decreasing axial pitch in the direction of fluid flow. U.S. Pat. No. 5,084,189 by inventor Harvey E. Richter exemplifies a Richter-type separator. The entire contents of U.S. Pat. No. 5,084,189 are herein incorporated by reference.

As used throughout this disclosure, a three-output Richter-type separator is defined as a Richter-type separator that separates solids in a water carrier into at least three components according to specific gravity. Examples of three-output Richter-type separators can be found in U.S. Patent Application No. 2012/0145633 and U.S. 2011/0147306 both to Polizzotti et al. Three-output Richter-type separators have primarily been used to separate oil from water and from heavier-than-water components such as sand or grit. Typical applications of the three-output Richter-type separators include oil spill cleanup, oil extraction, and oil/petroleum processing operations. To our knowledge, the inventor's experimental use at the Palm Beach County Western Region Wastewater Treatment Plant is the first actual use of a three-output Richter-type separator for separating lighter-than-water and heavier-than-water specific gravity solids from sanitary or municipal wastewater and in a municipal wastewater treatment plant.

During testing of the three-output Richter-type separator, the Inventor recognized unexpectedly, that he could combine the lighter-than-water and heavier-than-water specific gravity solids components of sanitary or municipal wastewater and gain sufficient solids concentration to feed the combination to a sludge de-watering device without any intermediary biological and sedimentation process. In addition, since the product water was sufficiently clear of solids that it could be feed directly to a membrane separator.

In addition to three-output Richter-type separators, the inventor envisions practicing aspects of his novel wastewater treatment systems and methods using other three-output axial-flow type separators that are capable of producing a combined lighter-than-water and heavier-than-water solids stream with sufficient solids concentration to directly feed a mechanical sludge-dewatering stage or otherwise capable of feeding a mechanical sludge-dewatering device without the need for intermediary biological-process-based system or sedimentation.

The inventor also envisions practicing aspects of his novel wastewater treatment systems and methods using three-output axial-flow type separators as described in existing wastewater treatment facilities where it may be desirable to leave some of the existing infrastructure in-place, for example, where sedimentation may be left as a pre-treatment.

An inherent property of the lighter-than-water solids stream is that some of the solids are an agglomeration of colloidal particles with air bubbles. Some of the individual particles may be heavier-than-water, but when agglomerated with the air bubbles, the agglomeration may form a lighter-than-water solid (i.e. the agglomeration may have a specific gravity of less-than-one). This agglomeration of air bubbles with colloidal particles that make up these solids occurs as a natural consequence of the mixing of air with colloidal particles in the wastewater stream. The agglomeration of air bubbles with colloidal particles can be purposely facilitated in order to increase the concentration of solids in the lighter-than-water solids stream. This can be accomplished by adding compressed air or other gasses into the inlet of the axial-flow type separator using a gas bubble injection device such as gas sparger or an atomizer.

DRAWINGS

FIG. 1 illustrates a block diagram of a conventional municipal wastewater treatment system typical in the prior art.

FIG. 2 illustrates a simplified block diagram of an improved municipal wastewater treatment system utilizing a three-output Richter-type separator and without any intermediary biological processes or sedimentation stages.

FIG. 3 illustrates a detailed block diagram of the improved municipal wastewater treatment system of FIG. 2.

FIG. 4 illustrates a simplified block diagram of an improved municipal wastewater treatment system of the present disclosure utilizing two three-output Richter-type separators connected in series with the lighter-than-water solids stream and heavier-than-water solids stream of the first three-output Richter-type separator combined and feeding the input of the second Richter-type separator.

FIG. 5 illustrates a three-output Richter-type separator of the present disclosure, in partial cutaway front elevation view, with the lighter-than-water and heavier-than-water solids output combined.

FIG. 6 illustrates a three-output Richter-type separator of the present disclosure, in partial cutaway front elevation view, with the lighter-than-water and heavier-than-water solids output combined and aided by an eductor.

FIG. 7 illustrates a simplified flow diagram of the present disclosure showing solids handling without any biological intermediately steps.

FIG. 8 illustrates a simplified flow diagram of the present disclosure showing adjusting the solids concentration by adjusting the flow of the input stream to the three-output Richter-type separator.

FIG. 9 illustrates a simplified flow diagram of the present disclosure showing adjusting the solids concentration by adjusting the flow of the partially clarified water stream.

FIG. 10 illustrates a simplified flow diagram of the present disclosure illustrating the water purification process without any intermediately biological-process or sedimentation steps.

FIG. 11 illustrates illustrate a simplified block diagram of an improved wastewater treatment system utilizing a three-output axial-flow type separator.

FIG. 12 illustrates a simplified flow diagram of the present disclosure showing solids handling without biological and sedimentation intermediary steps.

FIG. 13 illustrates a simplified flow diagram similar to FIG. 12 illustrating an additional step of a water purification process without any biological and sedimentation intermediately steps.

FIG. 14 illustrates the improved wastewater treatment system of FIG. 11 with the addition of a gas bubble injection device.

FIG. 15 illustrates a simplified flow diagram similar to FIG. 12 illustrating the additional step of injecting gas bubbles into the feed stream of the three-output axial-flow type separator of FIG. 14.

FIG. 16 illustrates the three-output axial-flow type separator as a three-output Richter-type separator and showing an air bubble injection system.

FIG. 17 illustrates a simplified block diagram similar to FIG. 11 showing the optional addition of surfactants to the partially clarified water stream and showing the filtration and disinfection stage in more detail.

FIG. 18 illustrates a more detailed block diagram of FIG. 11 incorporating features from FIGS. 14 and 17.

DETAILED DESCRIPTION

The following terms are used throughout this disclosure and are defined here for clarity and convenience.

Axial-flow type separator: as used throughout this disclosure, an axial-flow type separator is a defined as a centrifugal separation device for separating immiscible fluids, or solids in a fluid carrier, of different specific gravities by utilizing an axial-flow pump. An axial-flow pump is a centrifugal pump that uses an impeller that directs the flow of fluid axially rather than radially.

Three-output axial-flow type separator: As used throughout this disclosure, a three-output axial-flow type separator is defined as an axial-flow type separator that separates solids in a water carrier into at least three components according to specific gravity.

Municipal wastewater: as used throughout this disclosure, municipal wastewater is defined as disposed water from communities, such as cities or towns that flows through a sewage piping system and is treated at a municipal wastewater treatment plant. Municipal wastewater generally includes human feces, urine, hair, fibers, as well as food waste products. Municipal wastewater can include both domestic sewage, i.e. sewage from houses and apartments and spent water from commercial operations that are disposes of into the municipal sewage piping system. Municipal wastewater may also include storm water runoff that infiltrates into the sewage piping system.

Sanitary Wastewater: as used throughout this disclosure, sanitary wastewater, or sanitary sewage, is wastewater that includes biologically active solids such as human feces or food waste products.

Mechanical Sludge-Dewatering: as used throughout this disclosure, mechanical sludge-dewatering refers to apparatus or methods that use a dynamic mechanical mechanism, and not a biological mechanism or sedimentation, to remove sufficient amounts of water from the sludge to form sludge cake. Examples of mechanical sludge-dewatering devices include centrifuges, filter presses, belt presses, and thermal drying.

Biological-process and Biological-process system: as used throughout this disclosure, a biological-process or, a biological-process system, refers to methods or apparatus that uses either anaerobic or aerobic microorganisms to break down organic material in sanitary or municipal wastewater. Examples of biological-process-based systems include trickling filters, suspended growth process devices, aeration tanks, wastewater lagoons, constructed wetlands, and sludge digesters.

Sedimentation: as used throughout this disclosure, sedimentation refers to apparatus that uses gravity settling and surface skimming to remove suspended solids and floating solids from sanitary or municipal wastewater.

Lighter-than-water Solids Stream: as defined in this disclosure, a lighter-than-water solids stream is a resultant fluid stream from a three-output Richter-type separator or other three-output axial-flow type separators that includes water as the fluid carrier and where the solids within the fluid stream are lighter-than-water.

Heavier-than-water solids stream: as defined in this disclosure, a heavier-than-water solids stream is a resultant fluid stream from a three-output Richter-type separator or other three-output axial-flow type separators that includes water as the fluid carrier and where the solids within the fluid stream are heavier-than-water.

Partially clarified water stream: as defined in this disclosure, a partially clarified water stream is remaining stream that results from separating out the lighter-than-water solids and the heavier-than-water solids in a three-output Richter-type separator or other three-output axial-flow type separators.

The following description is made with reference to figures, where like numerals refer to like elements throughout the several views.

FIG. 1 illustrates a block diagram of a conventional municipal wastewater treatment system 10 typical in the prior art. As discussed in the Background section of this disclosure, one of the basic strategies in municipal and sanitary wastewater treatment is to remove or neutralize the contaminants and either dispose or reuse the resulting purified water. Municipal wastewater is typically composed of approximately 99.8% to 99.9% water. The other 0.1% to 0.2% of municipal wastewater includes contaminants such as grit, fats and oils, oxygen-demanding substances, pathogens, plant nutrients, inorganic chemicals, and synthetic organic chemicals. The conventional municipal wastewater treatment system 10 of FIG. 1 is a simplified diagram representative of a typical wastewater treatment plant. The conventional municipal wastewater treatment system 10 removes or neutralizes the contaminants though a typical multi-step process: pre-treatment 11, primary treatment 12, secondary treatment 13, tertiary treatment 14, and sludge treatment 15.

Pre-treatment 11 removes gross particulates and grit that can interfere with primary treatment 12 and secondary treatment 13 processes. Sand and grit can cause excessive wear of pumps and clog aeration devices. A bar screen 16 is typically used to remove these gross particulates. The bar screen 16 is typically constructed of parallel bars of steel or iron and inclined toward the flow of the wastewater. In FIG. 1, the raw sanitary wastewater 17 enters the pre-treatment 11 stage through an inlet pipe 18 into the bar screen 16. A grit chamber 19 removes grit, sand, coffee grounds, eggshells, and small rocks in the wastewater. Typically, the grit chamber 19 uses a vortex separator to separate grit from the wastewater. Vortex separators typical use a combination of gravity and centrifugal force. An example of an all-hydraulic vortex grit separator is sold by Hydro International under the registered trademark, GRIT KING®.

The primary treatment 12 stage typically uses gravity to remove heavier-than-water solids. This is accomplished by a process called sedimentation. In FIG. 1, this is accomplished in a primary clarifier 20 also known as a settling basin.

Secondary treatment 13 removes additional suspended solids and dissolved biodegradable material. This is typically accomplished using aerobic microorganisms to consume the soluble organic contaminants and other biodegradable material. In FIG. 1, this is accomplished using a combination of an aeration basin 21 and a secondary clarifier 22. Aeration basins are man-made ponds or basins that use artificially introduced air to promote the growth of aerobic microorganisms consume the organic matter in the wastewater. The aerated wastewater flows into the secondary clarifier 22, which is a sedimentation tank where the bio solids are removed by gravity settling.

Tertiary treatment 14 takes the product water from the secondary treatment and prepares it for reuse or for release into the environment. There are a number of possible strategies to tertiary treatment. In FIG. 1, the tertiary treatment 14 stage is a media filter 23. Media filters 23 are typically sand or carbon filter beds that can remove residual suspended solids and non-biodegradable organic compounds.

The sludge treatment 15 stage is illustrated as having two parts: a sludge digester 24 and sludge-dewatering 25. One of the goals of the sludge digester is to produce sufficient solids concentration in the sludge for the proper operation of the sludge-dewatering device. Sludge-dewatering devices typically require greater than 0.5% solids content. The sludge digester 24 uses microorganisms to digest and concentrate the solids. The thickened sludge 26 resulting from this operation typically has a solids concentration over 0.5% of solids to water.

This thickened sludge 26 is further dewatered as shown by the sludge-dewatering 25 block in FIG. 1. This is typically accomplished by sludge filter press or a sludge-dewatering centrifuge. The output of the sludge-dewatering 25 process, typically known as sludge cake 27, has approximately 15% to 35% solids to water concentration. The sludge cake 27 is typically hauled away 28 to be buried in a landfill or can be heat sterilized and used as fertilizer.

As late as Feb. 25, 2015, the inventor utilized a three-output Richter-type separator in a municipal wastewater treatment for experimental testing at the Palm Beach County Western Region Wastewater Treatment Plant in Pahokee, Fla. To our knowledge, the inventor's experimental use at the Palm Beach County Western Region Wastewater Treatment Plant is the first actual use of a three-output Richter-type separator for separating lighter-than-water and heavier-than-water specific gravity solids from sanitary or municipal wastewater and in a municipal wastewater treatment plant. The inventor recognized that by combining the lighter-than-water and heavier-than-water components, the output of Richter-type separator could be feed to a sludge press or sludge-dewatering centrifuge without any intermediary biological processes or sedimentation.

FIG. 2 illustrates a simplified block diagram of an improved municipal wastewater treatment system 100, as conceived by the inventor, utilizing a three-output Richter-type separator 101. The three-output Richter-type separator 101 includes three outputs that discharge a combination of water and solids according to the specific gravity of the solids. A first outlet port 102 discharges a lighter-than-water solids stream 103, a second outlet port 104 discharges a heavier-than-water solids stream 105, and a third outlet port 106 discharges a partially clarified water stream 107. The combination of the first outlet port 102 and the second outlet port 104 creates a combined stream 108. The combined stream 108 feeds a mechanical sludge-dewatering stage 109 without any intermediary biological-process-based system and without sedimentation. The output of the mechanical sludge-dewatering stage 109 is dewatered sludge, often referred to as sludge cake 110. The sludge cake 110 can optionally be subjected to a sterilization stage 111. The finished sludge cake 112 can be disposed by hauling away to a landfill, reused, or incinerated.

The partially clarified water stream 107 is clarified sufficiently to feed a filtration and disinfection stage 113 without any intermediary biological-process or sedimentation. The treated water 114 resulting from the filtration and disinfection stage 113 can be either disposed or reused. As illustrated in FIG. 2, the filtration wastewater 115 can be combined with mechanical sludge-dewatering wastewater 116 and the inlet wastewater 117 and feed into the Richter-type separator inlet 118.

In contrast to the conventional municipal wastewater treatment system 10 of FIG. 1, the improved municipal wastewater treatment system 100 of FIG. 2 does not require space and time consuming biological processes or sedimentation. This unexpected result and novel combination has the potential to significant reduce both construction, operational, and maintenance costs of municipal wastewater treatment operations. It is estimated that the facility footprint can advantageously be reduced to as small as 20% of a conventional municipal wastewater treatment facility.

The inventor envisions that the improved municipal wastewater treatment system 100 of FIGS. 2-4; the improved wastewater treatment system 150 of FIGS. 11, 14, 17, and 18; and the methods of FIGS. 7-10, 12, 13, 15, 17, and 18 could be adapted into existing wastewater treatment plants, food processing, or industrial facilities. Under some circumstances, it may be desirable because of cost or other reasons, to leave some of the sedimentation or biological process systems infrastructure in-place even though these components may be unnecessary. For example, sedimentation tanks or biological process systems may be positioned before the Richter-type separator inlet 118 of FIG. 1 or 4, or the axial-flow separator inlet 152 of FIG. 11, or 14.

Now, looking at the improved municipal wastewater treatment system 100 in more detail, we turn to FIG. 3 which illustrates a more detailed block diagram of the municipal wastewater treatment system of FIG. 2. Because biological processes and sedimentation are not required, it is not necessary to separately remove sand or grit. A grinder pump 119 can be used to reduce the size of gross particulates. The gross particulates along with the raw sanitary wastewater 120 sent to the three-output Richter-type separator 101. A feed pump 121 is placed between the grinder pump 119 and the three-output Richter-type separator 101 to control the rate of flow of wastewater to Richter-type separator.

As previously described, the combined stream 108 of the lighter-than-water solids stream 103 and the heavier-than-water solids stream 105 feeds the mechanical sludge-dewatering stage 109 without intermediary biological-process system and sedimentation. An optional eductor 122 can help facilitate the flow of lighter-than-water solids stream 103 into the heavier-than-water solids stream 105. Alternatively, a pump can optionally be used to help facilitate the flow of lighter-than-water solids stream 103. In FIG. 3, the mechanical sludge-dewatering stage 109 can be either a sludge filter press 123 or a sludge-dewatering centrifuge 124. Other equivalents mechanical sludge-dewatering equipment, such as belt filter presses, can be used. The resulting sludge cake 110 can optionally go through a sterilization stage 111 as previously describe. This sterilization stage 111 is typically some form of heat sterilization.

Polymers 125 can be optionally added to the inlet of the three-output Richter-type separator 101 to facilitate separation of suspended solids. Polymers 125 can also be optionally added to the inlet of the mechanical sludge-dewatering stage 109 to help facilitate dewatering of suspended solids. Polymers 125 coagulate suspended solids and produce large chains or curds of solid material know as floc that are easier to remove by centrifugal force.

Looking at the filtration and disinfection stage 113 in more detail, the partially clarified water stream 107 has a sufficiently low solids concentration to be directly filtered by a membrane filter 126 such as ultrafiltration or nanofiltration. Both ultrafiltration and nanofiltration are capable of filtering pathogens and suspended solids. In addition, nanofiltration can remove some of the valent ions. The membrane filter product water can be further treated by ultraviolet light 127 to remove the volatile BOD. Chemical disinfectant 128 such as chlorine and chloramines can be used to disinfectant the water.

The solids concentration can be controlled by varying the rate of flow to the three-output Richter-type separator 101, adjusting the speed of the impeller, or adjusting the ratio of the partially clarified water stream 107 to the feed water. A variable frequency drive (VFD) can be used to control the speed of the feed pump 121 and thereby the rate of flow to the three-output Richter-type separator. A VFD can also be used to control the speed of the motor of the three-output Richter-type separator 101. A control valve 130 can be used to control the ratio of partially clarified water stream to the input stream. Mass flow meters 129 dynamically measure the solids concentration at the input stream and the combined stream 108. Backpressure on the partially clarified water stream 107 and the heavier-than-water solids stream 105 can be adjusted by control valves 130 such as the electric control valves pictured. Other equivalent control valves can be used. Flow transmitters 131 measure the rate of heavier-than-water solids stream 105 and the partially clarified water stream 107. Flow transmitter can include, but are not limited to, magnetic flow meters, turbine flow meters, vortex flow meters, differential pressure flow meters, or paddle wheel flow meters. A control system 132 receives signals from the mass flow meters 129 and the flow transmitters 131 and adjusts the control valves 130 and VFDs according to a predetermined range of concentration ratios and output flows. The control signals between the control system 132 and the control valves 130 and the control system 132 and the VFDs can be analog, digital, wired, or wireless.

It may be desirable to gain a higher concentration of solids to feed the mechanical sludge-dewatering stage 109. FIG. 4 illustrates an embodiment of the present disclosure that can obtain higher solids concentrations feeding the mechanical sludge-dewatering stage 109 then the improved municipal wastewater treatment system 100 of FIGS. 2-3. In FIG. 4, this is achieved by connecting two of the three-output Richter-type separators 101 connected in series with the lighter-than-water solids stream 103 and heavier-than-water solids stream 105 of the first of the three-output Richter-type separators 101 form a combined stream 108 and feed the inlet 133 of the second of the three-output Richter-type separators 101. The second Richter-type separator lighter-than-water solids stream 134 and the second Richter-type separator heavier-than-water solids stream 135 form a second combined stream 136 and feed the mechanical sludge-dewatering stage 109. The sludge cake 110 that result from the output of the mechanical sludge-dewatering stage 109 can be optionally be subjected to a sterilization stage 111. The finished sludge cakes 112 can be disposed by hauling away to a landfill, reused, or incinerated as previously described.

The partially clarified water stream 107 of the first of the three-output Richter-type separators 101 is combined with a second partially clarified water stream 137 of the second of the three-output Richter-type separators forming a combined partially clarified water stream 138. The combined partially clarified water stream 138 feeds the filtration and disinfection stage 113 without any biological intermediary processes or sedimentation. The treated water 114 resulting from the filtration and disinfection stage 113 can be either disposed or reused. The filtration wastewater 115 is combined with mechanical sludge-dewatering wastewater 116 and the inlet wastewater 117 and feed into the Richter-type separator inlet 118.

FIGS. 5-6 illustrates a three-output Richter-type separator 101 of the present disclosure, in partial cutaway front elevation view. In FIG. 5, the first outlet port 102 and second outlet port 104 directly tied together. In FIG. 6 the flow of lighter-than-water solids stream 103 into the heavier-than-water solids stream 105 is aided by the optional eductor 122. Other than that, both FIGS. 5 and 6 are identical and both illustrate possible physical positions of the mass flow meters 129, flow transmitters 131, and control valves 130.

Referring to both FIGS. 5 and 6, the inlet wastewater 117 enters the Richter-type separator inlet 118. The Richter-type separator inlet 118 is illustrated as being inwardly co-axial to the axial-type pump housing 139. The three-output Richter-type separator 101 includes an impeller 140 and a body 141 extending longitudinally downstream from the impeller 140. The impeller 140 includes two or more helical blades 142 having decreasing axial pitch in a direction of fluid flow and defining a hollow core 143 that passes fluid and occupies a central axis of the impeller 140.

Because the impeller 140 has a hollow core 143, there is no central shaft to drive the impeller 140. In FIGS. 5-6, the impeller 140 is rigidly attached to a rotating drum surrounding the outer circumference of the impeller 140. The rotating drum is not shown but hidden beneath the drum housing 144. The drum, in turn is driven by a motor 145. The motor 145 illustrated is electric, however, the motor 145 can also be a hydraulic motor or water-driven motor.

As the inlet wastewater 117 passes through the hollow core 143 and the helical blades 142 of the impeller 140, a low-pressure area 146 in the center of the line of flow is initiated from the hollow core 143 with the lighter-than-water specific solids constituents. A higher velocity flow 147 tends toward the perimeter of the body 141. The higher velocity flow 147 includes water and heavier-than-water specific gravity constituents. The heavier-than-water constituents will discharge from the body 141 through the second outlet port 104. The third outlet port 106 will discharge the partially clarified water stream 107. The partially clarified water stream 107 can include dissolved and suspended solids with a specific gravity of one.

The lighter-than-water solids constituent flowing in the low-pressure area 146 is discharged through a hollow tube 148, forming the first outlet port 102. The hollow tube 148 is axial to the hollow core 143, inwardly co-axial to the body 141, extending longitudinally into the body 141, and positioned against the end of the body 141 distal to the impeller.

FIG. 7 illustrates a simplified flow diagram of the present disclosure showing solids handling. In step 201, the municipal or sanitary wastewater is separated into three streams by a three-output Richter-type separator, according to specific gravity: a lighter-than-water solids stream, a heavier-than-water solids stream, and a water stream. In step 202, the lighter-than-water solids stream, and the heavier-than-water solids stream are combined, creating a combined component stream. In step 203, the combined component stream is mechanically sludge dewatered without any biological or sedimentation intermediary steps.

FIG. 8 illustrates a simplified flow diagram of the present disclosure showing adjusting the solids concentration by adjusting the flow of the input stream to the three-output Richter-type separator. In step 204, the solids concentration of the combined component stream is determined. Referring to FIGS. 3 and 8, the solids concentration is calculated by the control system 132 using the mass flow meter 129. In step 205, the control system retrieves a predetermined range of acceptable solids concentration levels from memory. This could alternatively be a predetermined solids ratio determined by measuring the mass flow using the mass flow meter 129 positioned at the Richter-type separator inlet 118 and at the mechanical sludge-dewatering stage 109. In step 206, the calculated solids concentration from the mass flow meter measurement is compared with the predetermined range retrieved from memory. In step 207, if the solids concentration is below range, decrease the flowrate to the three-output Richter-type separator 101. If the solids concentration is above range, in step 208, increase the flowrate to the three-output Richter-type separator 101. If the solid concentration is within range, do not adjust the flowrate. The process loops back to the beginning.

FIG. 9 illustrates a simplified flow diagram of the present disclosure showing adjusting the solids concentration by adjusting the flow of the partially clarified water stream. Referring to FIGS. 3 and 9, in step 204, the solids concentration of the combined component stream is determined. Referring to FIGS. 3 and 8, the solids concentration is calculated by the control system 132 using the mass flow meter 129. In step 205, the control system retrieves a predetermined range of acceptable solids concentration levels from memory. This could alternatively be a predetermined solids ratio determined by measuring the mass flow using the mass flow meter 129 positioned at the Richter-type separator inlet 118 and at the mechanical sludge-dewatering stage 109. In step 206, the calculated solids concentration from the mass flow meter measurement is compared with the predetermined range retrieved from memory. In step 209, if the solids concentration determined in step 204 is below the expected range from step 205, then the flow of the partially clarified water stream 107 flowing from the third outlet port 106 is increased by sending a signal from the control system 132 to further open the control valve 130 associated with the third outlet port 106. In step 210, if the solids concentration determined in step 204 is above the expected range from step 205, then the flow of the partially clarified water stream 107 flowing from the third outlet port 106 is decreased by sending a signal from the control system 132 to further close the control valve 130 associated with the third outlet port 106.

FIG. 10 illustrates a simplified flow diagram of the present disclosure illustrating the water purification process without any biological and sedimentation intermediately steps. Referring to FIGS. 3 and 10, in step 201, the municipal or sanitary wastewater is separated into three streams by a three-output Richter-type separator 101, according to specific gravity: a lighter-than-water solids stream 103, a heavier-than-water solids stream 105, and a partially clarified water stream 107. In step 202, the lighter-than-water solids stream 103, and the heavier-than-water solids stream are combined, creating a combined stream 108. In step 211, filter the partially clarified water stream 107 with a membrane filter without any biological or sedimentation intermediary steps. In step 203, the combined component stream is mechanically sludge dewatered without any biological or sedimentation intermediary steps.

In addition to three-output Richter-type separators, the inventor envisions practicing the systems and methods described for FIGS. 2-10 with other three-output axial-flow type separator. This may include a three-out axial-flow type separator that includes a hollow core impeller to facilitate passing of wastewater particulates or three-out axial-flow type separator with non-hollow core impellers. Three-output axial-flow separators capable of being used for the described systems and methods of FIGS. 11-18 include a combined lighter-than-water and heavier-than-water solids stream with sufficient solids concentration to directly feed a mechanical sludge-dewatering stage without any intermediary biological-process-based system and without sedimentation. As previously described, mechanical sludge-dewatering devices, such as sludge presses or sludge-dewatering centrifuges, typically require solids concentrations of greater than 0.5%. Depending on the make and manufacture of the sludge-dewatering device, it may require a lower or higher concentration.

FIGS. 11, 14, and 17 illustrate a simplified block diagram of an improved wastewater treatment system 150, utilizing a three-output axial-flow type separator 151. FIGS. 12, 13, and 15 illustrate simplified flow diagram of the present disclosure corresponding to FIGS. 11, 14, and 17 respectively. Referring to FIGS. 11, 14, and 17, as with the three-output Richter-type separator 101 of FIG. 2, the three-output axial-flow type separator 151 includes three outlets that discharge a combination of water and solids according to the specific gravity of the solids. A first outlet port 102 discharges a lighter-than-water solids stream 103, a second outlet port 104 discharges a heavier-than-water solids stream 105, and a third outlet port 106 discharges a partially clarified water stream 107. The combination of the lighter-than-water solids stream 103 from the first outlet port 102 and heavier-than-water solids stream 105 from the second outlet port 104 creates a combined stream 108. The combined stream 108 feed a mechanical sludge-dewatering stage 109 without any intermediary biological-process-based system and without sedimentation. The output of the mechanical sludge-dewatering stage 109 is dewatered sludge, often referred to as sludge cake 110. The sludge cake 110 can optionally be subjected to a sterilization stage 111. The finished sludge cake 112 can be disposed by hauling away to a landfill, reused, or incinerated.

The partially clarified water stream 107 is clarified sufficiently to feed a filtration and disinfection stage 113 without any intermediary biological-process or sedimentation. The treated water 114 resulting from the filtration and disinfection stage 113 can be either disposed or reused. The filtration wastewater 115 can be combined with mechanical sludge-dewatering wastewater 116 and the inlet wastewater 117 and fed into the axial-flow separator inlet 152.

Corresponding processes are summarized in the simplified flow diagrams of FIGS. 12, 13, and 15. FIG. 12 illustrates a simplified flow diagram of the present disclosure showing solids handling without biological and sedimentation intermediary steps. FIG. 13 illustrates a simplified flow diagram of the present disclosure illustrating an additional step of a water purification process without any biological and sedimentation intermediately steps. FIG. 15 describes an additional step of injecting air bubbles into the feed stream. Referring to FIGS. 12, 13 and 15, in step 212, the municipal or sanitary wastewater is separated into three streams by a three-output axial-flow type separator, according to specific gravity: a lighter-than-water solids stream, a heavier-than-water solids stream, and a water stream. In step 202, the lighter-than-water solids stream, and the heavier-than-water solids stream are combined, creating a combined component stream. In step 203, the combined component stream is mechanically sludge dewatered without any biological or sedimentation intermediary steps. Referring to FIG. 13, in step 211, the partially clarified water stream 107 of FIGS. 11, 14, and 17 is sent to through a filtration device, such as with a membrane filter 126 of FIG. 17, without any biological or sedimentation intermediary steps.

As with the improved municipal wastewater treatment system 100 of FIG. 2, the improved wastewater treatment system 150 of FIGS. 11,14, 17, and 18 has the potential of reducing the size of a sanitary wastewater treatment facility to as little as 20% of a conventional municipal or sanitary wastewater treatment facility. In addition, the improved wastewater treatment system 150 has the potential to significant reduce both construction, operational, and maintenance costs of municipal, sanitary, and food product wastewater treatment operations.

As previously described, for FIGS. 2-10, the lighter-than-water solids stream includes water as the fluid carrier where solids within the fluid stream are lighter-than-water (i.e. solids, which can be an agglomeration of particles, within the fluid stream have a specific gravity of less-than-one as previously described). One of the ways that solids inherently may have a specific gravity of less-than-one is by virtue of the agglomeration of colloidal particles within the solid with air bubbles, which decreases the density of the combined mass. This agglomeration of air bubbles with colloidal particles that make up the solids occurs as a natural consequence of the mixing of air with colloidal particles in the wastewater stream. The agglomeration of air bubbles within the solids can be purposely facilitated in order to increase the concentration of solids in the lighter-than-water solids stream.

FIGS. 14-16 shows an enhancement to the improved wastewater treatment system 150 in order to purposely increase the agglomeration of air bubbles with solids within the wastewater. FIG. 14 illustrates the improved wastewater treatment system 150 of FIG. 11 with the addition of a gas bubble injection device 153 and compressed gas 154. The compressed gas 154 is typically air, but could also other gasses; for example, purified nitrogen gas, or a mixture of air and other gases. Air could be compressed using an air compressor. Alternatively, the compressed air, compressed nitrogen, or other gas composition, could be provided by a pressured tank. The remaining elements in FIG. 14 remain the same as described for FIG. 11.

FIG. 15 illustrates a simplified flow diagram of solids handling of the present disclosure with the additional step of injecting gas bubbles into the feed stream of the three-output axial-flow type separator 151 of FIG. 14. In step 213, the gas bubbles agglomerate with solids, reducing their specific gravity. This is analogous to a float or pontoon floating on water (i.e. having a specific gravity of less-than-one) because of the air filing the cavity within the otherwise heavier-than-water structure. The other steps of separating the wastewater into three steams (step 212), combining the fluid streams containing solids with specifically gravities greater-than-one and less than 1 (step 202), and mechanically watering the combined stream without any biological or sedimentation intermediary steps (step 203), is a previously described.

FIG. 16 illustrates the three-output axial-flow type separator 151 of FIG. 14, as a three-output Richter-type separator 101 and showing an air bubble injection system. In FIG. 16, compressed gas 154 is feed by way of a feed pipe 155 into the axial-flow separator inlet 152 using a gas bubble injection device 153. The gas bubble injection device 153 shown is a side mounted gas sparger. Other types of gas bubble injection devices 153, such as atomizers, side stream spargers, or inline gas spargers can also be used. The compressed gas 154 exits the gas bubble injection device 153 into the inlet wastewater 117 forming a quantity of gas bubbles 157 a. The gas bubbles 157 a that exit the gas bubble injection device 153 are small; typically less then 1 millimeter. As the gas bubbles 157 b enter the axial-type pump housing 139, which is larger than the diameter of the axial-flow separator inlet 152, the pressure drops, causing the air bubbles to expand. The gas bubbles 157 b mix with the solid masses and particulates and become agglomerated with the gas bubbles 157 b. Some of these solid masses and particulates that have a specific gravity greater-than-one without the air bubbles now have a specific gravity less-than-one and will enter the low-pressure area 146 of the stream after passing through either the helical blades 142 or the hollow core 143 of impeller 140. The remaining air bubbles 157 c will also collect in the low-pressure area 146. The material with a specific gravity of less-than-one will pass through the hollow tube 148 and exit out of the first outlet port 102 as the lighter-than-water solids stream 103.

A higher velocity flow 147 tends toward the perimeter of the body 141. The higher velocity flow 147 includes water and heavier-than-water specific gravity constituents. The heavier-than-water constituents will discharge from the body 141 through the second outlet port 104 as the heavier-than-water solids stream 105. The third outlet port 106 will discharge the partially clarified water stream 107. The partially clarified water stream 107 can include dissolved and suspended solids with a specific gravity of one.

The partially clarified water stream 107 can include nitrates. As illustrated in FIG. 17, surfactants 158 can be added to the partially clarified water stream 107 to help facilitate removal of the nitrates. The surfactants 158 are shown being mixed into the partially clarified water stream 107 using a pump 159. The control valve 130 can be used to control the flow of the partially clarified water stream 107. The mixture of partially clarified water stream 107 and surfactant 158 enter a membrane filter 126, such as an ultrafiltration or nanofiltration unit as previously described. The membrane filter may also be a micellar-enhanced ultrafiltration unit which is particularly adept for this purpose. The surfactants 158 bind the nitrates and do not allow them to pass through the membrane filter 126. The fluid filtered by the membrane can be further disinfected by ultraviolet light 127 and/or a chemical disinfectant 128. The output of the disinfection stage 113 is treated water 114 as previously discussed. The filtration wastewater 115, including the nitrates bound by the surfactants 158 are reintroduced back into the axial-flow separator inlet 152. Depending on the surfactant 158, the bound nitrate will be ejected out of the heavier-than-water solids stream 105 or lighter-than-water solids stream 103 and ultimately end up in the combined stream 108.

FIG. 18 illustrates a more detailed block diagram of FIG. 11 of the improved wastewater treatment system 150 incorporating features from FIGS. 14 and 17. Because biological processes and sedimentation are not required, it is not necessary to separately remove sand or grit. A grinder pump 119 can be used to reduce the size of gross particulates. The gross particulates along with the raw sanitary wastewater 120 sent to the three-output axial-flow type separator 151. A feed pump 121 can be placed between the grinder pump 119 and the three-output axial-flow type separator 151 to control the rate of flow of wastewater to three-output axial-flow separator.

As previously described, the combined stream 108 of the lighter-than-water solids stream 103 and the heavier-than-water solids stream 105 feeds the mechanical sludge-dewatering stage 109 without intermediary biological-process system and sedimentation. An optional eductor 122 can help facilitate the flow of lighter-than-water solids stream 103 into the heavier-than-water solids stream 105. The mechanical sludge-dewatering stage 109 can be a sludge filter press 123 or a sludge-dewatering centrifuge 124. Other equivalents mechanical sludge-dewatering equipment, such as belt filter presses, can be used. The resulting sludge cake 110 can optionally go through a sterilization stage 111 as previously described. This sterilization stage 111 is typically some form of heat sterilization. The finished sludge cake 112 can disposed by hauling away to a landfill, reused, or incinerated, for example.

Polymers 125 can be optionally added to the inlet of the three-output axial-flow type separator 151 to facilitate separation of suspended solids. Polymers 125 can also be optionally added to the inlet of the mechanical sludge-dewatering stage 109 to help facilitate dewatering of suspended solids. Polymers 125 coagulate suspended solids and produce large chains or curds of solid material know as floc that are easier to remove by centrifugal force. A gas bubble injection device 153, position after the polymers 125 are injected, introduces air bubbles into inlet wastewater 117. The air bubbles agglomerate with some of the solids, increasing the lighter-than-water solids concentration. The gas bubble injection device 153 is shown using compressed gas 154, as described for FIG. 14.

Looking at the filtration and disinfection stage 113 in more detail, the partially clarified water stream 107 has a sufficiently low solids concentration to be directly filtered by a membrane filter 126 such as ultrafiltration or nanofiltration, or micellar-enhanced ultrafiltration unit. The ultrafiltration, nanofiltration, and micellar-enhanced ultrafiltration unit are capable of filtering pathogens and suspended solids. In addition, nanofiltration can remove some of the valent ions. The micellar-enhanced ultrafiltration unit can be used in combination with surfactants 158 to filter nitrates. The surfactants 158 are shown being introduced into the partially clarified water stream 107 by the pump 159, as previously described for FIG. 17. The membrane filter product water can be further treated by ultraviolet light 127 to remove the volatile BOD. Chemical disinfectant 128 such as chlorine and chloramines can be used to disinfectant the water.

As previously described, the solids concentration can be controlled by varying the rate of flow to the three-output axial-flow type separator 151, adjusting the speed of the impeller, or adjusting the ratio of the partially clarified water stream 107 to the feed water. A VFD can be used to control the speed of the feed pump 121 and thereby the rate of flow to the three-output Richter-type separator. A VFD can also be used to control the speed of the motor of the three-output axial-flow type separator 151. A control valve 130 can be used to control the ratio of partially clarified water stream 107 to the input stream. Mass flow meters 129 dynamically measure the solids concentration at the input stream and the combined stream 108. Backpressure on the partially clarified water stream 107 and the heavier-than-water solids stream 105 can be adjusted by control valves 130 such as the electric control valves pictured. Other equivalent control valves can be used. Flow transmitters 131 measure the rate of heavier-than-water solids stream 105 and the partially clarified water stream 107. Flow transmitter can include, but are not limited to, magnetic flow meters, turbine flow meters, vortex flow meters, differential pressure flow meters, or paddle wheel flow meters. A control system 132 receives signals from the mass flow meters 129 and the flow transmitters 131 and adjusts the control valves 130 and VFDs according to a predetermined range of concentration ratios and output flows. The control signals between the control system 132 and the control valves 130 and the control system 132 and the VFDs can be analog, digital, wired, or wireless.

A system and method for treating sanitary and municipal wastewater has been described. It is not the intent of this disclosure to limit the claimed invention to the examples, variations, and exemplary embodiments described in the specification. Features such as the disinfection stage 113 of FIG. 2-4, 11, 14, or 17 may not be required in all implementations. Similarly, feeding back the mechanical sludge-dewatering wastewater 116 and the filtration wastewater 115 with the inlet wastewater 117 may be helpful in some implementations but also may not required. These stages and features are shown for illustrative purposes to aid the reader in understanding possible helpful variations and implementations. Their existence does not imply that they are essential features. Those skilled in the art will recognize that variations will occur when embodying the claimed invention in specific implementations and environments. For example, it is possible to implement certain features described in separate embodiments in combination within a single embodiment. Similarly, it is possible to implement certain features described in single embodiments either separately or in combination in multiple embodiments. It is the intent of the inventor that these variations fall within the scope of the claimed invention. While the examples, exemplary embodiments, and variations are helpful to those skilled in the art in understanding the claimed invention, it should be understood that, the scope of the claimed invention is defined solely by the following claims and their equivalents. 

What is claimed is:
 1. A system for treating sanitary wastewater, comprising: a three-output axial-flow type separator including a first outlet port discharging a lighter-than-water solids stream, a second outlet port discharging a heavier-than-water solids stream, and a third outlet port discharging a partially clarified water stream; a mechanical sludge-dewatering device; the lighter-than-water solids stream and the heavier-than-water solids stream in combination creates a combined stream that feeds the mechanical sludge-dewatering device; and the combined stream having a solids concentration capable of feeding the mechanical sludge-dewatering device without intermediary biological-process systems.
 2. The system of claim 1, wherein the combined stream having the solids concentration capable of feeding the mechanical sludge-dewatering device without intermediary sedimentation devices.
 3. The system of claim 1, wherein the combined stream feeds the mechanical sludge-dewatering device without intermediary biological-process systems.
 4. The system of claim 1, further including a membrane filter receiving the partially clarified water stream.
 5. The system of claim 4, wherein: the three-output axial-flow type separator includes an inlet; the membrane filter discharges a filtration wastewater; and the filtration wastewater feeds into the inlet.
 6. The system of claim 1, further including: the three-output axial-flow type separator includes an inlet to receive inlet wastewater; and a gas bubble injection device positioned to inject gas bubbles into the inlet wastewater.
 7. A method for treating sanitary wastewater, comprising: creating a combined stream by combining a lighter-than-water solids stream and a heavier-than-water solids stream from corresponding first and second outlets of a three-output axial-flow type separator; and sludge-dewatering the combined stream using a mechanical sludge-dewatering device, the combined stream having solids concentration capable of feeding the mechanical sludge-dewatering device without intermediary biological-process systems.
 8. The method of claim 7, wherein the solids concentration capable of feeding the mechanical sludge-dewatering device without intermediary sedimentation devices.
 9. The method of claim 7, further including sludge-dewatering the combined stream without intermediary biological processes systems.
 10. The method of claim 7, further comprising: processing a partially clarified water stream discharged from the three-output axial-flow type separator through a membrane filter.
 11. The method of claim 7, further comprising: determining the solids concentration of the combined stream; retrieve a solids concentration predetermined range; and dynamically change an input flow rate to the three-output axial-flow type separator based on comparing the solids concentration of the combined stream and the solids concentration predetermined range.
 12. The method of claim 7, further comprising: determining the solids concentration of the combined stream; retrieve a solids concentration predetermined range; and dynamically change a flow rate of a partially clarified water stream discharged from the three-output axial-flow type separator, based on comparing the solids concentration of the combined stream and the solids concentration predetermined range.
 13. The method of claim 7, further comprising: adding polymers to an inlet of the three-output axial-flow type separator to facilitate discharge of suspended solids.
 14. The method of claim 7, further comprising: receiving a sanitary wastewater stream into the three-output axial-flow type separator; and injecting gas bubbles into the sanitary wastewater stream before the sanitary wastewater stream enters the three-output axial-flow type separator. 